1. Field of the Invention
The present invention relates to a gas purification apparatus and method, and more particular, to a gas purification apparatus for removing fine particles entrained in a gas flow.
2. Description of the Related Art
A semiconductor device fabricated on a wafer substrate is formed thereon with wirings of several tens nm width. If fine particles of several tens nm size are adhered to the wirings, short circuit or other problems can be caused.
Thus, there is a strong demand to remove particles from a semiconductor device fabrication apparatus, especially from a substrate processing apparatus in which plasma etching is performed on wafers. As a removal apparatus for effectively removing gaseous impurities or fine particles, there has been developed, for example, a removal apparatus including a wet removal unit and two filters made of filter materials having different densities (see, for example, Japanese Laid-open Patent Publication No. 2002-35524).
A substrate processing apparatus includes a fan filter unit as an apparatus for supplying atmospheric air while removing particles. The fan filter unit is disposed in a transfer chamber space of a loader module. The chamber space is a mini environment isolated from a surrounding environment and small in volume in comparison with a clean room.
The fan filter unit includes a fan for generating a gas flow directed from a surrounding environment (external environment) toward the internal space of the transfer chamber. The fan filter unit also includes a filter made of an aggregate of mesh-like fibers. The filter of the fan filter unit traps and removes particles mixed in the gas flow and larger in size than the mesh size.
However, the filter of the conventional fan filter unit such as an ULPA (ultra low penetration air filter) or a HEPA (high efficiency particulate air filter) has a mesh size of several hundreds nm, and cannot remove particles of several tens nm size, which cause short circuit or other problems in a semiconductor device.
Though it is possible to remove particles of several tens nm size by means of a filter in which the mesh size is made small, such a filter is low in conductance and causes a reduction in the efficiency of gas supply into the internal space of the transfer chamber.